Where Are the Children? by Mary Higgins Clark

Nancy Harmon long ago fled the heartbreak of her first marriage, the macabre deaths of her two little children, and the shocking charges against her. She changed her name, dyed her hair, and left California for the windswept peace of Cape Cod. Now remarried, she has two more beloved children, and the terrible pain has begun to heal -- until the morning when she looks in the backyard for her little boy and girl and finds only one red mitten. She knows that the nightmare is beginning again....